Mount for steering gear box

ABSTRACT

A steering gear box mount includes a resilient member interposed between a motor vehicle body and a steering gear box for allowing movement of the steering gear box. The mount also has a structure for limiting allowed movement of the steering gear box. The structure includes a mechanism for selectively rigidly fixing the steering gear box to a motor vehicle body, or a mechanism for continuously adjusting the allowed movement of the steering gear box.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mount for supporting a steering gearbox on a motor vehicle body.

2. Description of the Relevant Art

In automobiles, it is general practice to mount a steering gear box onan automobile body through a damping member such as of rubber in orderto prevent external forces such as a lateral wind or a road shock frombeing transmitted as vibration to a steering wheel while the automobileis traveling.

Where such a mount structure is employed, however, the maneuvering orsteering response is somewhat lowered since the steering gear box issupported on the automobile body with relatively low rigidity. If thesteering gear box were rigidly secured to the automobile body, thesteering response would be increased, but external forces would be morelikely transmitted to the steering wheel.

The present invention has been made to meet both of the abovecontradictory requirements for mounting a steering gear box on a motorvehicle body. In other words, the present invention increases thesteering response and also prevents external forces from beingtransmitted to a steering wheel.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a steering gearbox mount comprising a steering gear box, a motor vehicle body, a firstresilient member interposed between the motor vehicle body and a portionof the steering gear box for allowing the steering gear box to move, andmeans interposed between the motor vehicle body and another portion ofthe steering gear box for limiting the allowed movement of the steeringgear box.

It is an object of the present invention to provide a mount forsupporting a steering gear box on a motor vehicle body, the mount beingcapable of changing the rigidity with which the steering gear box issupported on the motor vehicle body.

The supporting rigidity of the mounted according to the presentinvention may be varied continuously, or may be varied between twostates, i.e., a movable state and a fixed state.

The above and further objects, details and advantages of the presentinvention will become apparent from the following detailed descriptionof preferred embodiments thereof, when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a front steering gear box supported on amotor vehicle body by a mount according to a first embodiment of thepresent invention, the view also showing components coupled to the frontsteering gear box and a control system for a supporting rigidityadjusting device;

FIG. 2 is an enlarged fragmentary elevational view, partly in crosssection, of the mount of FIG. 1;

FIG. 3 is a schematic view of a front steering gear box supported on amotor vehicle body by a mount according to a second embodiment of thepresent invention;

FIG. 4 is an enlarged cross-sectional view of the mount of FIG. 3;

FIG. 5 is an enlarged cross-sectional view of a mount according to athird embodiment of the present invention;

FIG. 6 is a schematic view of a front and rear wheel steering apparatus;

FIG. 7 is a schematic view of a rear steering gear box and componentscoupled thereto, the rear steering gear box being supported on a motorvehicle body by the mount of the first embodiment;

FIG. 8 is a schematic view of a control system for a supporting rigidityadjusting device for the mount of the first embodiment, the controlsystem being incorporated in a front and rear wheel steering apparatus;and

FIGS. 9(a) and 9(b) are schematic veiws of a modified directionalcontrol valve arrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, a steering wheel 1 of a motor vehicle such as anautomobile is coupled to a steering shaft 2 connected to a pinion shaft4 of a rack-and-pinion steering gear box 3. A rack shaft 5 (FIG. 2)extending and movable laterally through the gear box 3 has opposite endsjoined by respective tie rods 8 to knuckle arms 7 on which respectivefront wheels 6 are supported. The gear box 3 comprises two members 3a,3b coupled to each other. The member 3a is mounted on a motor vehiclebody B through a rubber damper 9 (or first resilient member) and a metalband 10. The gear box 3 is allowed by the rubber damper 9 to move to acertain extent with respect to the motor vehicle body B.

The other member 3b of the steering gear box 3 has a radial arm 11 bywhich a device 20 for adjusting the supporting rigidity of the gear box3 is mounted. More specifically, as shown in FIG. 2, a support pin 12 isslidably inserted transversely through the radial arm 11. The supportpin 12 has opposite ends supported on legs 13a, 13b of a bifurcatedbracket 13 fixed to the motor vehicle body B. The support pin 12 islocked against rotation by means of a stopper 14 disposed on the outerside of one of the legs 13a. The radial arm 11 has a cylinder 21 definedin its distal end portion and extending perpendicularly to the supportpin 12. The support pin 12 has a partly spherical recess 22 defined in aportion thereof facing into the cylinder 21. A steel ball 23 is housedin the cylinder 21 and has a peripheral portion seated in the recess 22.The cylinder 21 also houses a piston 24 having a partly spherical recess24a in which another peripheral portion of the steel ball 23 isreceived. The cylinder 21 has an opening in which a plug 25 is threaded,with a compression coil spring 26 interposed between the plug 25 and thepiston 24.

Two compression coil springs 16 are interposed between the radial arm 11and the legs 13a, 13b of the bracket 13.

The cylinder 21 is connected to an oil supply/discharge passage 29. Theoil supply/discharge passage 29 is generally shown in FIG. 1 as beingcoupled to the radial arm 11, and more specifically shown in FIG. 2 asbeing coupled to the plug 25. The supporting rigidity adjusting device20 thus constructed is controlled in its operation by a control system30.

As illustrated in FIG. 1, the control system 30 includes a directionalcontrol valve 36 connected between the oil supply/discharge passage 29and another oil supply/discharge passage 35 through which oil underpressure flows from a pump 32 driven by an engine 31. The directionalcontrol valve 36 is shifted in its position by a solenoid 38 which isselectively energized and de-energized by a manual switch 37. When thedirectional control valve 36 is in the illustrated position (FIG. 1),the oil under pressure is supplied from the passage 35 through thepassage 29 into the cylinder 21. When the directional control valve 36is shifted to the left, the oil under pressure is returned from thecylinder 21 via an oil passage 39 into an oil tank 33. The directionalcontrol valve 36 may be automatically shifted dependent on the speed oftravel of the motor vehicle. The oil under pressure thus employed in thecontrol system 30 is introduced from a power steering device or the likeof the motor vehicle.

When the oil under pressure is supplied into the cylinder 21, the piston24 is moved forwardly to press the steel ball 23 into the recess 22 forthereby more rigidly securing the steering gear box 3 to the motorvehicle body B. Therefore, the steering response may be thus increasedfor better maneuverability especially in medium- and low-speed ranges ofthe motor vehicle.

As the oil under pressure is discharged from the cylinder 21, the steelball 23 remains seated in the recess 22 only under the resiliency of thecoil spring 26. Therefore, the steering gear box 3 is movable to acertain extent with respect to the motor vehicle body B under theresiliency of the coil spring 26, the coil springs 16, and the rubberdamper 9. External forces applied to the motor vehicle can thus beabsorbed by the steering gear box 3, allowing the motor vehicle to runstraight particularly in a high-speed range.

As will be understood from the foregoing, portions of the supportingridigity adjusting device 20, including the support pin 12, the stopper14, the cylinder 21 defined in the radial arm 11, the recess 22 in pin12, the ball 23, the piston 24 and the plug 25, function as means forselectively fixing the radial arm 11 to the vehicle body through thesupport bracket 13.

FIGS. 3 and 4 show a gear box mount according to a second embodiment ofthe present invention. While in the first embodiment the supportingrigidity with which the gear box is mounted on the motor vehicle body isadjustable in two states, i.e., a movable state and a fixed state, thesupporting rigidly is continuously variable in the second embodiment.

As illustrated in FIG. 3, a steering gear box 43 accommodating a rackand pinion (not shown) therein has an end 43a near a pinion shaft 42coupled to a steering wheel 41. The end 43a of the steering gear box 43is mounted on a motor vehicle body B by a metal band 46 with a rubberdamper 45 interposed therebetween. Therefore, the steering gear box 43is movable to a certain extent with respect to the motor vehicle body B.

The steering gear box 43 has a radial arm 47 near the opposite end 43bthereof. Between the radial arm 47 and the motor vehicle body B, thereis interposed a device 40 for adjusting the supporting rigidity of thegear box 43, the device 40 including a bracket 51 secured to the motorvehicle body B. The bracket 51 has an upstanding wall 52 extending thesecured based thereof substantially parallel to the radial arm 47 of thegear box 43. A screw shaft 53 extends through and between the upstandingwall 52 and the radial arm 47.

As clearly shown in FIG. 4, the screw shaft 53 has external screwthreads 54 over the entire length thereof, and includes an end portion53a (shown on the lefthand side in FIG. 4) extending from the upstandingwall 52 remotely from the radial arm 47. An actuator 50 comprising anelectric motor for axially moving the shaft 53 has a rotor 55 havinginternal screw threads 56 threaded over the end portion 53a of the screwshaft 53. The rotor 55 of the motor 50 comprises an iron core 57 andarmature windings 58 wound around the iron core 57. The rotor 55 alsoincludes a commutator 61 positioned at the outer (left) end of the rotor55 and fixed to the iron core 57. The motor 50 has a housing 59 servingas a stator and permanent magnets 60 fixed to the inner peripheralsurface of the housing 59. The permanent magnets 60 are spaced from theouter peripheral surface of the rotor 50 by a small gap. The housing 59supports thereon brushes 62 held in contact with the commutator 61 atall times. The housing 59 is fastened to the bracket 51 by a bolt 63.

The wall 52 of the bracket 51 has a hole 64 defined therethrough andthrough which the shaft 53 extends. A sleeve 65 is fitted in the hole 64and has an extension 65a extending to a position near the radial arm 47of the gear box 43. A rubber damper 66A is fitted over the sleeveextension 65a, the rubber damper 66A being tapered to the right towardthe radial arm 47.

The shaft 53 has an opposite end portion 53b remote from the end portion53a and on which a sleeve 67 is mounted. A rubber damper 66B which istapered to the left toward the radial arm 47 is fitted over the sleeve67. The sleeve 67 has a flange 68 on its outer end (on the righthandside as shown). The end portion 53b has a shaft end projecting beyondthe flange 68, with a nut 69 threaded over the shaft end. The shaft 53extends through and is movable through the sleeves 65, 67.

The rubber damper 66A on the sleeve 65 and the rubber damper 66B on thesleeve 67 cooperate with each other in sandwiching the radial arm 47therebetween. The radial arm 47 has opposite recesses 49 havingrespective inner peripheral surfaces 49a flaring outwardly for pressedengagement with the tapered ends of the rubber dampers 66A, 66B. Theradial arm 47 also includes a web 48 serving as a common bottom of therecesses 49 and having a hole 48a through which the shaft 53 extendswith a clearance therearound.

The supporting rigidity adjusting device 40 thus constructed operates asfollows: The motor 50 may be manually started or automatically starteddependent on the running conditions of the motor vehicle. When the motor50 is started, the rotor 55 is rotated to cause the threads 56 thereofengaging with the threads 54 of the shaft 53 to move the shaft 53axially. The sleeve 67 supporting the rubber damper 66B is prevented bythe nut 69 from moving to the right (FIG. 4) on the shaft 53. Therefore,when the shaft 53 is moved to the left, the sleeve 67 is also moved tothe left with the shaft 53, reducing the distance between the flange 68of the sleeve 67 and the wall 52 of the bracket 51. The rubber dampers66A, 66B with the radial arm 47 sandwiched therebetween are elasticallycompressed to continuously increase the rigidity with which the radialarm 47 is supported on the bracket 51. Upon reverse rotation of therotor 55, the shaft 53 is axially moved to the right (FIG. 4) forthereby causing the flange 68 to be pressed against the nut 69 under theresiliency of the rubber dampers 66A, 66B. The flange 68 is thereforemoved with the shaft 53, increasing the distance between the flange 68and the wall 52. The rigidity of the rubber dampers 66a, 66B is nowprogressively lowered.

In the second embodiment as described above, in order for the rigidityof the rubber dampers 66A, 66B by which the gear box 43 is resilientlysupported on the motor vehicle body B to be continuously variable, theflange or movable member 68 held against the rubber dampers is disposedon only one side of the radial arm 47 of the gear box 43. Therefore, asthe movable member 68 is moved, the rubber dampers 66A, 66B are pressedor released on only one side thereof, and the radial arm 47 of the gearbox 43 which is located centrally between the rubber dampers 66A, 66B ismoved upon compression and expansion of the rubber dampers 66A, 66B.Consequently, the gear box 43 is slightly moved along the shaft 43 eachtime the rigidity of the rubber dampers 66A, 66B is adjusted.

According to a third embodiment shown in FIG. 5, two movable members aredisposed outwardly of a pair of rubber dampers, respectively,sandwiching therebetween a radial arm integral with a gear box, and aremovable back and forth on a shaft while holding the radial arm in asubstantially central position therebetween at all times through therubber dampers. Thus, the gear box is prevented from moving when therigidity of the rubber dampers is adjusted. More specifically, as shownin FIG. 5, a radial arm 72 is integrally formed with a steering gear box71, which is supported by the radial arm 72 on a motor vehicle body. Adevice 80 for adjusting the supporting rigidity of the gear box isinterposed between the radial arm 72 and the motor vehicle body. Thedevice 80 includes a bracket 81 fixed to the motor vehicle body andextending substantially perpendicular to the radial arm 72. The bracket81 has two upstanding walls 82A, 82B spaced equidistantly from andpositioned on the opposite sides of the radial arm 72. A screw shaft 83extends through the walls 82A, 82B and the radial arm 72.

The screw shaft 83 has threaded portions 84, 85 which are externallythreaded in opposite directions, the threaded portion 84 extending fromone end (righthand end in FIG. 5) of the shaft 83 through the wall 82Ato the radial arm 72 and the other threaded portion 85 extending fromthe radial arm 72 to and beyond the wall 82b. Sleeves 86, 87 arethreaded over the threaded portions 84, 85, respectively, the sleeves86, 87 having radially outward flanges 88, 89, respectively, on theirintermediate portions. The sleeves 86, 87 extending respectively throughthe walls 82A, 82B and are slidable with respect thereto throughrespective plain bearings 90. The plain bearings 90 are held in positionby separate bearing holders 91, respectively, fixed by bolts 92 to thewalls 82A, 82B. The flanges 88, 89 are positioned between the radial arm72 and the walls 82A, 82B, i.e., on the opposite sides of the radial arm72. The flanges 88, 89 have ends 88a, 89a, respectively, extending insliding contact with the surface of the bracket 81 for preventing thesleeves 86, 87 from rotating around the shaft 83. The flanges 88, 89have shallow annular cavities 93, 94, respectively, defined in theirsurfaces facing the radial arm 72 and extending around the sleeves 86,87. The annular cavities 93, 94 receive therein the bottoms of thickrubber dampers 95A, 95B which are fitted over the sleeves 86, 87,respectively, and tapered toward the radial arm 72. The radial arm 72has opposite recesses 96, 97 capable of receiving the distal ends of therubber dampers 95A, 95B, respectively, and a web 98 serving as a commonbottom of the recesses 96, 97 and having a hole 98a through which theshaft 83 extends with a sufficient clearance therearound.

The shaft 83 has an axial extension 99 on its opposite end (lefthand endin FIG. 5) portion, the extension 99 being disposed in an electric motor110 which serves as an actuator for rotating the shaft 83 about its ownaxis. The extension 99 has a step or flange 100 on its end adjacent tothe threaded portion 85 and is externally threaded on its outer end 101.The motor 110 has an iron core 111 fitted over the extension 99 andhaving one end held against the step 100. The iron core 111 is securedto the shaft 83 for rotation therewith by a key 102 inserted to theopposite outer end thereof, and is prevented from axially moving by anut 103 threaded over the threaded end 101 of the shaft extension 99with a washer 104 interposed between the nut 103 and the iron core 111.Armature windings 112 are wound around the iron core 111, and acommutator 113 is mounted on the iron core 111 near its outer end.Permanent magnets 117 are fixed to the inner peripheral surface of amotor housing 114 secured to the bracket 81 by means of a bolt 115 witha washer 116 disposed between the bolt 115 and the bracket 81. Brushes118 are supported on the housing 114 in sliding contact with thecommutator 113. Ball bearings 119 and outer seal members 120 areinterposed between the motor housing 114 and the iron core 111.

When the motor 110 is started, the shaft 83 is rotated about its ownaxis with the iron core 111. The sleeves 86, 87 threaded over thethreaded portions 84, 85, respectively, are now moved toward or awayfrom each other. The rubber dampers 95A, 95B interposed between theflanges 88, 89 with the radial arm 72 therebetween are compressedagainst or released from the opposite sides of the radial arm 72 whichacts as a positional reference, so that the rigidity of the rubberdampers 95A, 95B are continuously adjusted or varied.

In the second and third embodiments, the two rubber dampers are employedas a resilient body. However, a single rubber damper may be employed.The actuator for varying the ridigity of the rubber dampers may be ofany desired form.

The mount structure with variable supporting rigidity, as describedabove in the three embodiments, may be employed for supporting a rearsteering gear box as well as a front steering gear box of a motorvehicle with steerable front and rear wheels. A system arrangement inwhich the mount structure of the invention is incorporated in a motorvehicle with steerable front and rear wheels will be described below.

FIG. 6 schematically shows a front and rear wheel steering apparatus. Asteering shaft 122 coupled to a steering wheel 121 is connected to apinion shaft 124 in a rack-and-pinion front steering gear box 123. Thefront steering gear box 123 houses a rack shaft 125 movable laterallytherein and having opposite ends coupled by tie rods 128 to knuckle arms127 on which respective front wheels 126 are rotatably supported. Thefront steering gear box 123 also has an output pinion shaft 129 fortransmitting a steering force to a rear wheel steering mechanism, thepinion shaft 129 meshing with the rack shaft 125.

Rear wheels 131 are rotatably supported respectively on knuckle arms 132coupled by tie rods 133 to the opposite ends of a joint member 134movably disposed in a rear steering gear box 135. The gear box 135 hasan input shaft 136 having an eccentric shaft 137 on its inner endengaging an engaging member 138 on the joint member 134. Rotation of theinput shaft 136 is converted by the eccentric shaft 137 and the engagingmember 138 to linear motion of the joint member 134 in the transversedirection of the motor vehicle. The output shaft 129 and the input shaft136 are operatively interconnected by a linkage shaft 139.

The front steering gear box 123 is supported on the motor vehicle bodyin the same manner as shown in FIGS. 1 and 2, and the mount structureitself for supporting the front steering gear box 123 is the same asthat shown in FIGS. 1 and 2.

As illustrated in FIG. 7, the rear steering gear box 135 is mounted atone end thereof on the motor vehicle body B for relative movement withrespect thereto through a rubber damper 140. The rear steering gear box135 has a radial arm 141 near the opposite end thereof. The radial arm141 is laterally slidable on a support pin 142 supported by a bifurcatedbracket 143 with coil springs 146 interposed between the bracket 143 andthe radial arm 141.

A supporting rigidity adjusting device 160 which is identical instructure to the device shown in FIG. 2 is disposed between the radialarm 141 and the support pin 142. The device 160 is connected to an oilsupply/discharge passage 161.

FIG. 8 shows a control system 170 for controlling supporting rigidityadjusting devices 150, 160 for the front and rear steering gear boxes.Oil under pressure from an oil pump 172 driven by a motor 171 flowsthrough oil supply/discharge passages 175, 179 between which there isconnected a directional control valve 176 that can be shifted by asolenoid 178 controlled by a control unit 177. When the directionalcontrol valve 176 is in the illustrated position, oil under pressure issupplied into a cylinder 152 of the front adjusting device 150 and oilunder pressure flows from a cylinder 162 of the rear adjusting device160 via the oil passage 179 back into an oil tank 173. When thedirectional control valve 176 is in the lower position, oil underpressure is supplied to the rear adjusting device 160 and oil underpressure is removed from the front adjusting device 150. The oil underpressure used in the control system of FIG. 8 may be introduced from apower steering device or the like.

The control unit 177 is supplied with speed information from a car speedsensor 181. When the motor vehicle runs in a low- or medium-speed rangebelow a prescribed speed, the control unit 177 issues an output signalto keep the directional control valve 176 in the illustrated position.When the motor vehicle travels in a high-speed range higher than theprescribed speed, the directional control valve 176 is shifted to andheld in the lowered position by the control unit 177.

FIGS. 9(a) and 9(b) show a modified directional control valvearrangement. Two oil supply passages 175A, 175B extend from the oilpump, and two oil return passages 179A, 179B extend to the oil tank. Afirst directional control valve 176A is connected between the oil supplyand return passages 175A, 179A for a front adjusting device 150' havinga cylinder 152', and a second directional control valve 175B isconnected between the oil supply and return passages 175B, 179B for arear adjusting device 160' having a cylinder 162'. The first and seconddirectional control valves 176A, 176B are separately controlled by thecontrol unit.

While the front and rear steering mechanisms are mechanicallyinterlinked in the embodiment of FIG. 6, the principles of the presentinvention are also applicable to a motor vehicle having a rear steeringmechanism which is electrically or hydraulically controlled on the basisof the speed of travel of the motor vehicle and a front steering angle.

With the supporting rigidity adjusting device of the invention beingincorporated in the motor vehicle with steerable front and rear wheels,the rigidity with which the front wheels are supported can be increasedat a speed lower than a prescribed speed setting, and the rigidity withwhich the rear wheels are supported can be increased at a speed equal toor higher than the prescribed speed setting. Therefore, the motorvehicle can be turned more efficiently and smoothly in low- andmedium-speed ranges, and can travel straight more stably in a high-speedrange. As a consequence, the motor vehicle with steerable front and rearwheels and a supporting rigidity adjusting device according to thepresent invention can perform its intended capability highlyeffectively.

Although there have been described what are at present considered to bethe preferred embodiments of the present invention, it will beunderstood that the invention may be embodied in other specific formswithout departing from the spirit or essential characteristics thereof.The present embodiments are therefore to be considered in all aspects asillustrative, and not restrictive. The scope of the invention isindicated by the appended claims rather than by the foregoingdescription.

We claim:
 1. A steering gear box mount comprising:a steering gear box; a motor vehicle body; a first resilient member interposed between said motor vehicle body and a portion of said steering gear box for allowing said steering gear box to move; and means interposed between said motor vehicle body and another portion of said steering gear box for limiting allowed movement of said steering gear box, said means including a mechanism for selectively securing said steering gear box to said motor vehicle body; said mechanism including support means fixed to said motor vehicle body for supporting said another portion of said steering gear box so as to be movable relative to said support means, and means for selectively fixing said another portion of said steering gear box to said support means; said motor vehicle body supports a steering gear box for front wheels and a steering gear box for rear wheels, said steering gear box mount supporting at least one of said steering gear boxes; and said means for limiting allowed movement of said steering gear box limits allowed movement of said steering gear box for the front wheels to a larger extent than allowed movement of said steering gear box for the rear wheels at a vehicle speed lower than a prescribed speed, and limits allowed movement of said steering gear box for the rear wheels to a larger extent than allowed movement of said steering gear box for the front wheels at a vehicle speed higher than the prescribed speed.
 2. A steering gear box mount according to claim 1, wherein:said support means comprises a support bracket fixed to said vehicle body, a support pin having a recess formed therein and extending through said bracket and through said another portion of said steering gear box, and said fixing means is moveable and selectively fixable with respect to said recess of said support pin.
 3. A steering gear box mount comprising:a motor vehicle body with steerable front and rear wheels; a front steering gear box for said front wheels; a rear steering gear box for said rear wheels; and supporting rigidity adjusting means interposed between said motor vehicle body and each of said front and rear steering gear boxes for adjusting rigidity in supporting said steering gear boxes; and control means for controlling said supporting rigidity adjusting means to increase the rigidity in supporting one of said front and rear steering gear boxes relative to the rigidity in supporting the other of said front and rear steering gear boxes dependent on a vehicle speed.
 4. A steering gear box mount according to claim 2, wherein:said control means increases the rigidity in supporting said front steering gear box greater than the rigidity in supporting said rear steering gear box at a vehicle speed lower than a prescribed speed.
 5. A steering gear box mount according to claim 3, wherein:said control means increases the rigidity in supporting said rear steering gear box greater than the rigidity in supporting said front steering gear box at a vehicle speed higher than a prescribed speed. 